The aim of this project is to determine the effects of lesions of anterior or posterior cingulate cortex on "animal hypnosis" (tonic immobility) in the rabbit. In addition other rabbits will be given lesions of the various subdivisions of the amygdala and tested for tonic immobility. Rabbits with these lesions will also be tested in active and passive avoidance. In previous research we have found that hippocampal and septal lesions increase tonic immobility. These results have been explained in terms of the inhibitory response modulating functions of the limbic system. If this explanation is correct, and if the anterior cingulate gyrus is a response facilitatory region, then its ablation should attenuate tonic immobility. Lesions of the amygdala may either increase or decrease the response depending upon the relative importance of the response inhibiting or emotional functions of this region. Tonic immobility is offered as an unlearned emotional behavior which has wide species generality and is influenced by the limbic system. It is suggested that this response could serve as a model emotional behavior produced by the "older" portions of the brain and is therefore worth further physiological studies.